In recent years, semiconductors and semiconductor processing techniques have been used to form "micromechanical" devices. Examples of micromechanical devices are accelerometers, digital micro-mirror devices (DMDs), gears, motors, and pumps, among many other mechanical devices.
In the case of DMDs, for example, an array of hundreds or thousands of tiny tilting mirrors is fabricated. To permit the mirrors to tilt, each is attached to one or more hinges mounted on support posts, and spaced by an air gap over underlying control circuitry. The control circuitry provides electrostatic forces, which cause each mirror to selectively tilt. Examples of DMDs are disclosed in U.S. Pat. No. 4,662,746, entitled "Spatial Light Modulator and Method," herein incorporated by reference.
As the term "micro-mechanical" implies, micro-mechanical devices have tiny mechanical elements that are designed to move. However, these moveable elements are delicate, and care must be taken not to damage them during the manufacturing process. One danger comes from impurities from the air, such as dust, which can settle on the movable elements and inhibit or prevent their movement. Another danger comes from airflow at the surface of these elements, which can cause them to move beyond their breaking point or to be dislodged. Therefore, efforts are made during processing of such devices to control the fabrication environment to reduce air contamination and airflow.
In a typical manufacturing process, micro-mechanical devices and associated circuitry are formed on semiconductor wafers. Copies of the same circuitry are fabricated on different areas of a wafer as "dies". After fabrication is completed, the dies are separated from each other. The dies are then picked up with a vacuum device and transferred to the packaging process.
In existing manufacturing processes, this step of picking up dies with a vacuum has resulted in significant airflow or suction at the face of the die, causing damage to the micro-mechanical elements. To reduce such damage, prior systems have reduced vacuum pressure, which results in less effective pick-up and may even cause some dies to be dropped. Also, attempts have been made to use mechanical "grabbers" to move the dies. Although these mechanical systems reduce airflow, they can be complex and difficult to maintain.